Explosion-forming processes and apparatus



y 21, 1968 E. AMlNl ETAL 3,383,889

EXPLOSION-FORMING PROCESSES AND APPARATUS Filed Nov. 5, 1964 2 Sheets-Sheet l May 21, 1968 E. AMINI ETAL EXPLOSION-FORMING PROCESSES AND APPARATUS 2 Sheets-Sheet 2 Filed Nov. 5, 1964 United States Patent 3,383,889 EXPLOSION-FORMING PROCESSES AND APPARATUS Ehssanollah Amini, Sutton Coltliield, Stephen Albert Tobias, Birmingham, and Geoifrey Hohson, Manchester, England, assignors to National Research Development Corporation, London, England, a British corporation Filed Nov. 3, 1964, Ser. No. 408,576 Claims priority, application Great Britain, Nov. 4, 1963, 43,500/63 7 Claims. (Cl. 72-56) ABSTRACT OF THE DISCLOSURE An explosion-forming machine comprising an annular cutting die for cutting a blank from a deformable workpiece; means for mounting a deformable workpiece in spaced relation to said cutting die, said means including clamping means for clamping the edges of the workpiece; a forming die disposed on the opposite side of said cutting die from said mounting means for receiving a blank cut from the workpiece by said cutting die; and means for explosively producing an impulse wavefront, said means being disposed on the opposite side of said mounting means from said cutting die whereby the impulse will deform the workpiece against said cutting die to cut a blank therefrom and Will project the blank against said forming die.

This invention relates to explosion-forming of materials, and particularly of sheet metal. Development of techniques for explosion-forming processes, in which intense shock waves produced by detonation of an explosive charge cause deformation of a workpiece, has followed somewhat conventional lines and the process is now used quite extensively for the shaping of sheet metal or for the forming or consolidation of material, possibly a metal powder compact. The pressure pulse resulting from the detonation is of short duration and the peak pressure on the workpiece, besides depending upon the size of the charge, depends upon the distance of the charge from the workpiece. In general, the pressure distribution is found to be the better, the more incompressible the medium; so that best results are usually obtained if the medium is a liquid, and water is normally used, such processes being carried out in an open water tank. An explosion-forming machine has been proposed in co-pending patent application No. 300,749, now Patent No. 3,289,447, however, in which the forming operation is carried out in a closed space, thereby, besides providing other advantages, enabling the processes to be carried out under work-shop conditions.

The present invention is directed to providing an improved technique for use, for example, with any of the known types of apparatus.

An explosion-forming process in accordance with the invention, is adapted to subject a workpiece to at least one impulsive force such as to provide a formed product with one or more holes therethrough of pre-determined position and configuration. Thus the hole(s) may be formed directly as a result of a severing operation, or indirectly as a result of weakening of part(s) of the workpiece such that it(they) may be readily removed by a simple subsequent operation. Preferably the severing or weakening operation is carried out prior to the forming operation.

Thus a workpiece may be arranged to receive an impulse wavefront to move part thereof towards a die, and one or more projections in association with said die may be arranged to contact the moving part during 3,333,889 Patented May 21, 1968 the forming movement thereof so as to weaken the material of the part in predetermined position(s) and in predetermined configuration(s) so as to leave the said part in such state, as aforesaid, that holes may be readily formed in the said part after extraction from the'forming machine. Alternatively, and preferably the projections may be arranged to weaken the material to such a degee as to causesevering and so that the formed part has the designed holes therein prior to removal from the die.

In one embodiment of the invention in a forming machine, a die is provided having suitably shaped projections there-from and/or reliefs therein and the machine is so arranged that the impulsive forces, impinging on the workpiece first sever a blank from the workpiece, then cause said blank to be forced into and/or against the die with itsprojections and/or reliefs, to result in the formation of a shaped product with weakened or severed hole portions as desired.

One embodiment of the invention will now be described, by way of example, with reference to the use of an explosion-forming machine of-the kind described in the specification accompanying patent application No. 300,749.

FIGURE 1 of the accompanying drawings shows a central vertical section through part of the machine; FIGURES 2 and 3 show plan view and a sectional view respectively, of the product obtained by use of the die members shown in FIGURE 1.

In the drawing, the metal workpiece 2 is clamped by means shown between an annular orifice member 3 and a backing member 4, which forms a flange to the die chamber 11 in which the die member 5 is seated. A ring 8 mounted on the die member 5 has its edge so shaped that, when the metal of the workpiece 2 is moved under the influence of the shock wave(s), a blank is severed from the workpiece. The shock wave is derived from the firing of an explosive mechanism 13, as described in the specification accompanying co-pending application No. 3003749, within a pulse shaping part 14. The part 14 is held against the orifice member 3- by means of bolts 15, nuts on which engage flange 4 and a top member 16 to clamp the two together.

In use, when the workpiece 2 has been clamped in position, as shown, the part 14 is brought up to the die chamber and clamped in position with an O-ring 17 sealing the joint between part 14 and the orifice member 3; the workpiece is now ready for the change to be exploded. Under the influence of the shock wave(s) from the explosion the blank that is severed from the workpiece moves, still under the influence of the shock wave(s) against the die member 5. The die member is shaped to give a finished form of the blank, but projecting from the face of the die are a plurality of projections 6 and 7, whose edges are shaped to cause severance of material from the blank. The projections may be parts of inserts in the main die member, or stuck to the surface of the member or may be simply placed on it, though care has to be taken in the latter case that they are not dislodged by the shock wave(s). Parts of the blank in its motion impinge against these projections, with the result that holes are punched out of the blank as it moves into contact with the die face proper. The projections 6 can, for instance, provide for the formation of clearance holes for bolts or the like and the hole caused by projection 7 can be of special shape, such as the hexagonal shape shown, for particular purposes. The die chamber can be evacuated, if necessary, using holes, or slots, 9 and connection 10. Projections and/or reliefs may also be provided on the die surface for the formation of sti fening ribs, decorative patterns, trade marks and other features.

By suitable positioning and choice of shape and the extent of the projections and/or reliefs, it is possible to arrive at a situation where the blank is formed as a finished product with features which would otherwise have had to have been produced by one or more subsequent operations. The fact that such subsequent operation(s) has(have) to be carried out on shaped material after the normal forming operation has usually rendered such subsequent -operation(s) very awkward to perform.

It is not essential, from the point of view of the invention, that a blank should first 'be removed from the workpiece; it is obvious that the invention is applicable also where the edge of the workpiece is retained by the clamping operation which the centre part is acted upon in the same way as described with reference to the blank. It is also obvious that the shape of the workpiece, or blank, need not be of symmetrical contour in cross section; it is to be understood that the part of the forming operation in accordance with the invention may arise from inertia developed in the workpiece, or the blank, by the initial shock wave(s).

What we claim is:

1. An explosion-forming process comprising disposing a deformable workpiece in spaced relationship to a forming die and clamping the edge port-ions of said workpiece against movement toward said forming die, severing a blank from the workpiece by deforming the workpiece against a cutting die with an explosively generated impulse, and projecting the severed blank through the cutting die and against a forming die by said impulse thereby shaping the blank to the contours of said forming die, the edges of the blank being uninhibited against movement during the shaping operation by virtue of having been cut away from the remainder of the workpiece.

2. A method as in claim 1 wherein at least one hole is cut in said blank when said blank is projected against said forming die.

3. A method as in claim 1 wherein a portion of pre- 4 determined configuration of said blank is weakened when said blank is projected against said forming die whereby 'said portion may be removed subsequently by simple means to provide a hole in the blank.

4. An explosionforming machine comprising a cutting die for cutting a blank from a deformable workpiece; means for mounting a deformable workpiece in spaced relation to said cutting die, said means including clamping means for clamping the edges of the workpiece; a forming die disposed on the opposite side of said cutting die from said mounting means for receiving a blank cut from the workpiece by said cutting die; and means for explosively producing an impulse wavefront, said means being disposed on the opposite side of said mounting means from said cutting die whereby the impulse will deform the workpiece against said cutting die to cut a blank therefrom and will project the blank against said forming die.

5. A method as in claim 1 wherein a hole-making operation on the severed blank is at least commenced prior to the shaping operation by providing at least one projection on the forming die arranged to contact the moving blank.

6. Apparatus as in claim 4 wherein said forming die includes means for carrying out a hole-making operation on the blank, said means comprising at least one projection extending therefrom toward said cutting die and presenting a free end which is contacted by the blank.

7. Apparatus as in claim 6 wherein the free end of said projection is hexagonal.

References Cited UNITED STATES PATENTS 2,133,445 10/1938 Guerin 72--55 2,377,664 6/1945 Berger 72--55 2,385,083 9/1945 Kemerer 72-56 3,068,822 12/1962 Orr et a1. 72-56 3,228,222 1/1966 Maier 72-56 RICHARD J. HERBST, Primary Examiner. 

